Semiconductor light-emitting device and method for manufacturing thereof

ABSTRACT

In a semiconductor light-emitting device, on an n-GaAs substrate are stacked an n-GaAs buffer layer, an n-cladding layer, an undoped active layer, a p-cladding layer, a p-intermediate band gap layer and a p-current diffusion layer. Further, a first electrode is formed under the n-GaAs substrate, and a second electrode is formed on the grown-layer side. In this process, a region of the p-intermediate band gap layer just under the second electrode is removed, the p-current diffusion layer is stacked in the removal region on the p-cladding layer, and a junction plane of the p-current diffusion layer and the p-cladding layer becomes high in resistance due to an energy band structure of type II. This semiconductor light-emitting device is capable of reducing ineffective currents with a simple construction and taking out light effectively to outside, thus enhancing the emission intensity.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a semiconductor light-emittingdevice having a current diffusion layer and method for manufacturethereof.

[0002] In recent years, LEDs (Light-Emitting Diodes), which aresemiconductor light-emitting devices, have been in the limelight asindoor/outdoor display devices. In particular, with their trend towardhigher brightness, the outdoor display market has been rapidly expandingwhile LEDs have been growing as a medium to replace neon signs.High-brightness LEDs of visible range in such fields have been developedby AlGaInP-based DH (Double Hetero) type LEDs. FIGS. 25A, 25B, 25C showa top view, a sectional view and a functional view, respectively, of ayellow-band AlGaInP-based LED as a semiconductor light-emitting device.

[0003] In this semiconductor light-emitting device, as shown in FIGS.25A and 25B, an n-GaAs buffer layer 301 (thickness: 0.5 μm, Si doping:5×10¹⁷ cm⁻³), an n-AlGaInP cladding layer 302 (thickness: 1.0 μm, Sidoping: 5×10¹⁷ cm⁻³), an undoped (Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)Pactive layer 303 (thickness: 0.6 μm), a p-AlGaInP cladding layer 304(thickness: 0.7 μm, Zn doping: 5×10¹⁷ cm⁻³), a p-AlGaAs currentdiffusion layer 305 (thickness: 6 μm, Zn doping: 3×10¹⁸ cm⁻³), and ap-GaAs cap layer 306 (thickness: 0.1 μm, Zn doping: 3×10¹⁸ cm⁻³) aregrown on an n-GaAs substrate 310 by MOCVD process, and a first electrode311 is formed on the substrate side while a second electrode 312 isformed on the grown layer side. Regions of the p-GaAs cap layer 306other than a device center region thereof opposed to the grown-layerside second electrode 312 have been removed. In this semiconductorlight-emitting device, having a pn junction formed within the activelayer 303, light emission is generated by recombination of electrons andholes. With this semiconductor light-emitting device molded into 5 mmdia. resin, when a 20 mA current was passed therethrough, the resultantemission intensity was 1.5 cd.

[0004] In this semiconductor light-emitting device, as shown in FIG.25C, a current injected from the grown-layer side second electrode 312expands within the p-AlGaAs current diffusion layer 305, being injectedinto the active layer 303, where most part of the current flows to theregion under the second electrode 312. As a result, light emission overthe region under the second electrode 312 is intercepted by the secondelectrode 312 so as not to go outside, resulting in an ineffectivecurrent. This leads to a problem that the emission intensity would belower.

[0005] Thus, as an solution to this problem, there has been proposed astructure in which a current blocking layer for blocking the current isintroduced under the second electrode 312.

[0006] FIGS. 26A-26C show a top view, a sectional view and a functionalview, respectively, of a semiconductor light-emitting device having thestructure in which the current blocking layer is introduced. In thissemiconductor light-emitting device, as shown in FIGS. 26A and 26B, ann-GaAs buffer layer 321 (thickness: 0.5 μm, Si doping: 5×10¹⁷ cm⁻³), ann-AlGaInP cladding layer 322 (thickness: 1.0 μm, Si doping: 5×10¹⁷cm⁻³), an undoped (Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 323(thickness: 0.6 μm), a p-AlGaInP cladding layer 324 (thickness: 0.7 μm,Zn doping: 5×10¹⁷ cm⁻³), a p-AlGaInP intermediate band gap layer 325(thickness: 0.15 μm, Zn doping: 2×10¹⁸ cm⁻³), a p-GaP first currentdiffusion layer 326 (thickness: 1.5 μm, Zn doping: 1×10¹⁸ cm⁻³), ann-GaP current blocking layer 327 (thickness: 0.4 μm, Si doping: 3×10¹⁸cm⁻³), and a p-GaP second current blocking layer 328 (thickness: 6 μm,Zn doping: 2×10¹⁸ cm⁻³) are grown on an n-GaAs substrate 330 by MOCVDprocess, and a first electrode 331 is formed on the substrate side whilea second electrode 332 is formed on the grown layer side.

[0007] In this semiconductor light-emitting device, the n-GaP currentblocking layer 327 is subjected to etching removal with its devicecenter region left, and the second current diffusion layer 328 isre-grown thereon.

[0008] In this semiconductor light-emitting device, as shown in FIG.26C, a current injected from the grown-layer side second electrode 332,avoiding the n-GaP current blocking layer 327 provided under the secondelectrode 332, flows to both sides of the n-GaP current blocking layer327. As a result, as compared with the semiconductor light-emittingdevice shown in FIG. 25, this semiconductor light-emitting deviceinvolves less ineffective current that flows to under the secondelectrode 332, resulting in increased emission intensity. With thissemiconductor light-emitting device applied to a 5 mm dia. moldedarticle, the emission intensity at a 20 mA current conduction was 2.0cd, an increase of slightly more than 30% as compared with thesemiconductor light-emitting device shown in FIG. 25. However, becausethe thickness of the p-GaP first current diffusion layer 326 providedunder the n-GaP current blocking layer 327 is as thick as 1.5 μm, thereis still a sneak current going to under the n-GaP current blocking layer327 as shown in FIG. 26C. Thus, there is a problem that the ineffectivecurrent is not eliminated completely.

SUMMARY OF THE INVENTION

[0009] Accordingly, an object of the present invention is to provide asemiconductor light-emitting device, as well as a method for manufacturethereof, which can be reduced in ineffective current with a simpleconstruction and can effectively take out light to outside.

[0010] In order to achieve the above object, there is provided asemiconductor light-emitting device comprising: a first-conductive-typefirst cladding layer, a first-conductive-type or second-conductive-typeor an undoped active layer, a second-conductive-type second claddinglayer, a second-conductive-type intermediate band gap layer and asecond-conductive-type current diffusion layer, all of which are stackedon one side of a surface of a first-conductive-type semiconductorsubstrate, a first electrode formed on the other side of the surface ofthe first-conductive-type semiconductor substrate, and a secondelectrode formed partly on the second-conductive-type current diffusionlayer, wherein

[0011] a region of the second-conductive-type intermediate band gaplayer just under the second electrode is removed, and thesecond-conductive-type current diffusion layer is stacked in the removalregion on the second-conductive-type second cladding layer, and wherein

[0012] a junction plane of the second-conductive-type current diffusionlayer and the second-conductive-type second cladding layer has an energyband structure of type II.

[0013] With this semiconductor light-emitting device having the aboveconstitution, in the removal region of the second-conductive-typeintermediate band gap layer, since the junction plane of thesecond-conductive-type current diffusion layer and thesecond-conductive-type second cladding layer becomes high in resistancedue to the energy band structure of type II, the current flows to aroundthe removal region, allowing ineffective currents flowing under thesecond electrode formed partly on the second-conductive-type currentdiffusion layer to be reduced so that the emission intensity isenhanced. It is noted that the first electrode formed on the other sideof the surface of the first-conductive-type semiconductor substrate maybe either a partial electrode or a full electrode.

[0014] Also, there is provided a semiconductor light-emitting devicecomprising: a first-conductive-type first cladding layer, afirst-conductive-type or second-conductive-type or an undoped activelayer, a second-conductive-type second cladding layer, asecond-conductive-type intermediate band gap layer and asecond-conductive-type current diffusion layer, all of which are stackedon one side of a surface of a first-conductive-type semiconductorsubstrate, wherein

[0015] a device center region of the second-conductive-type intermediateband gap layer is removed, and the second-conductive-type currentdiffusion layer is stacked in the removal region on thesecond-conductive-type second cladding layer,

[0016] the second-conductive-type current diffusion layer and thesecond-conductive-type second cladding layer have an energy bandstructure in which an upper-end position of valence band and a lower-endposition of conduction band are in a type II relation, and wherein

[0017] the semiconductor light-emitting device further comprises a firstelectrode formed overall on the other side of the surface of thefirst-conductive-type semiconductor substrate, and a second electrodeformed over the device center region on the second-conductive-typecurrent diffusion layer.

[0018] With this semiconductor light-emitting device having the aboveconstitution, in the removal region of the second-conductive-typeintermediate band gap layer at the device center region, since thejunction plane of the second-conductive-type current diffusion layer andthe second-conductive-type second cladding layer becomes high inresistance due to the energy band structure of type II, the currentflows to around the removal region, allowing ineffective currentsflowing under the second electrode formed at the device center region onthe second-conductive-type current diffusion layer to be reduced so thatthe emission intensity is enhanced.

[0019] In one embodiment of the present invention, an upper-side portionof a region of the second-conductive-type second cladding layercorresponding to the removal region of the second-conductive-typeintermediate band gap layer is removed.

[0020] With the semiconductor light-emitting device of this embodiment,both the removal region at the device center region of thesecond-conductive-type intermediate band gap layer and the region wherethe upper-side portion of the second-conductive-type second claddinglayer opposed to the removal region has been removed become high inresistance, and besides the high-resistance interface of thesecond-conductive-type current diffusion layer and thesecond-conductive-type second cladding layer is near the active layer.Thus, the ineffective currents flowing under the second electrode canfurther be reduced so that the emission intensity is further enhanced.

[0021] Also, there is provided a semiconductor light-emitting devicecomprising: a first-conductive-type first cladding layer, afirst-conductive-type or second-conductive-type or an undoped activelayer, a second-conductive-type second cladding layer, asecond-conductive-type etching stop layer, a second-conductive-typethird cladding layer, a second-conductive-type intermediate band gaplayer and a second-conductive-type current diffusion layer, all of whichare stacked on one side of a surface of a first-conductive-typesemiconductor substrate, wherein

[0022] device center regions of the second-conductive-type intermediateband gap layer and the second-conductive-type third cladding layer areremoved, respectively, and the second-conductive-type current diffusionlayer is stacked in the removal regions on the second-conductive-typeetching stop layer,

[0023] the second-conductive-type current diffusion layer, thesecond-conductive-type etching stop layer and the second-conductive-typesecond cladding layer have an energy band structure in which anupper-end position of valence band and a lower-end position ofconduction band are in a type II relation, and wherein

[0024] the semiconductor light-emitting device further comprises a firstelectrode formed overall on the other side of the surface of thefirst-conductive-type semiconductor substrate, and a second electrodeformed over the device center region on the second-conductive-typecurrent diffusion layer.

[0025] With the semiconductor light-emitting device having thisconstitution, the removal regions of the device center region where thesecond-conductive-type intermediate band gap layer and thesecond-conductive-type third cladding layer have been removed becomehigh in resistance due to the fact that an energy band structure inwhich the upper-end position of the valence band and the lower-endposition of the conduction band are in the type II relation is formed inthe second-conductive-type current diffusion layer, the etching stoplayer and the second cladding layer. Besides, the high-resistanceinterface can be formed near the active layer with high controllabilityby the presence of the second-conductive-type etching stop layer. Thus,there can be fabricated a semiconductor light-emitting device less inineffective currents and high in emission intensity with a good yield.

[0026] In one embodiment of the present invention, the removal region atthe device center region of the second-conductive-type intermediate bandgap layer and the second electrode have generally identicalconfigurations and are opposed to each other.

[0027] With the semiconductor light-emitting device of this embodiment,the emission efficiency can be optimized by the arrangement that thegrown-layer side second electrode and the high-resistance region underthe second electrode, both having generally equivalent configurations,are opposed to each other. Thus, the ineffective currents can belessened and the emission intensity can be enhanced.

[0028] Also, there is provided a semiconductor light-emitting devicecomprising: a first-conductive-type first cladding layer, afirst-conductive-type or second-conductive-type or an undoped activelayer, a second-conductive-type second cladding layer, asecond-conductive-type intermediate band gap layer and asecond-conductive-type current diffusion layer, all of which are stackedon one side of a surface of a first-conductive-type semiconductorsubstrate, wherein

[0029] a region of the second-conductive-type intermediate band gaplayer other than its device center region is removed, and thesecond-conductive-type current diffusion layer is stacked in the removalregion on the second-conductive-type second cladding layer,

[0030] the second-conductive-type current diffusion layer and thesecond-conductive-type second cladding layer have an energy bandstructure in which an upper-end position of valence band and a lower-endposition of conduction band are in a type II relation, and wherein

[0031] the semiconductor light-emitting device further comprises a firstelectrode formed overall on the other side of the surface of thefirst-conductive-type semiconductor substrate, and a second electrodeformed over the region other than the device center region on thesecond-conductive-type current diffusion layer.

[0032] With the semiconductor light-emitting device having thisconstitution, at the removal region where the region of thesecond-conductive-type intermediate band gap layer other than its devicecenter region has been removed, the junction plane of thesecond-conductive-type current diffusion layer and thesecond-conductive-type second cladding layer having the energy bandstructure of the type II becomes high in resistance. Thus, the currentflows to the device center region and, as a result, ineffective currentsflowing under the second electrode formed over the region other than thedevice center region on the second-conductive-type current diffusionlayer can be reduced, so that the emission intensity is enhanced.

[0033] In one embodiment of the present invention, an upper-side portionof the region of the second-conductive-type second cladding layeropposed to the removal region of the second-conductive-type intermediateband gap layer is removed.

[0034] With the semiconductor light-emitting device of this embodiment,both the removal region of the second-conductive-type intermediate bandgap layer other than its device center region and the region where theupper-side portion of the second-conductive-type second cladding layeropposed to the removal region has been removed become high inresistance, and besides the high-resistance interface of thesecond-conductive-type current diffusion layer and thesecond-conductive-type second cladding layer is near the active layer.Thus, the ineffective currents flowing under the second electrode canfurther be reduced so that the emission intensity is further enhanced.

[0035] Also, there is provided a semiconductor light-emitting devicecomprising: a first-conductive-type first cladding layer, afirst-conductive-type or second-conductive-type or an undoped activelayer, a second-conductive-type second cladding layer, asecond-conductive-type etching stop layer, a second-conductive-typethird cladding layer, a second-conductive-type intermediate band gaplayer and a second-conductive-type current diffusion layer, all of whichare stacked on one side of a surface of a first-conductive-typesemiconductor substrate, wherein

[0036] regions of the second-conductive-type intermediate band gap layerand the second-conductive-type third cladding layer other than theirdevice center regions are removed, respectively, and thesecond-conductive-type current diffusion layer is stacked in the removalregions on the second-conductive-type etching stop layer,

[0037] the second-conductive-type current diffusion layer, thesecond-conductive-type etching stop layer and the second-conductive-typesecond cladding layer have an energy band structure in which anupper-end position of valence band and a lower-end position ofconduction band are in a type II relation, and wherein

[0038] the semiconductor light-emitting device further comprises a firstelectrode formed overall on the one side of the surface of thefirst-conductive-type semiconductor substrate, and a second electrodeformed over the region other than the device center region on thesecond-conductive-type current diffusion layer.

[0039] With the semiconductor light-emitting device of thisconstitution, the removal regions other than the device center regionswhere the regions of the second-conductive-type intermediate band gaplayer and the second-conductive-type third cladding layer have beenremoved become high in resistance due to the fact that an energy bandstructure in which the upper-end position of the valence band and thelower-end position of the conduction band are in the type II relation isformed in the second-conductive-type current diffusion layer, etchingstop layer and second cladding layer, and besides the high-resistanceinterface can be formed with high controllability near the active layerby the presence of the second-conductive-type etching stop layer. Thus,there can be fabricated a semiconductor light-emitting device less inineffective currents and high in emission intensity with a good yield.

[0040] In one embodiment of the present invention, a protective layer ofthe second conductive type is formed on the second-conductive-typeintermediate band gap layer.

[0041] With the semiconductor light-emitting device of this embodiment,since the second-conductive-type protective layer is present on thesecond-conductive-type intermediate band gap layer, there is noresistance layer of the interface with the current diffusion layerformed on the second-conductive-type protective layer. Thus, theoperating voltage can be lowered.

[0042] In one embodiment of the present invention, thefirst-conductive-type semiconductor substrate is made of GaAs,

[0043] the first-conductive-type first cladding layer, thefirst-conductive-type or second-conductive-type or undoped active layerand the second-conductive-type second cladding layer are made of anAlGaInP-based compound semiconductor that provides lattice matching withGaAs,

[0044] the second-conductive-type current diffusion layer is made of aGaP- or AlGaInP-based compound semiconductor, and

[0045] the second-conductive-type intermediate band gap layer is made ofan AlGaInP-based compound semiconductor.

[0046] With the semiconductor light-emitting device of this embodiment,ineffective currents can be reduced so that an AlGaInP-basedsemiconductor light-emitting device of high emission intensity can berealized.

[0047] In one embodiment of the present invention, thefirst-conductive-type semiconductor substrate is made of GaAs,

[0048] the first-conductive-type first cladding layer, thefirst-conductive-type or second-conductive-type or undoped active layer,the second-conductive-type second cladding layer, thesecond-conductive-type etching stop layer and the second-conductive-typethird cladding layer are made of an AlGaInP-based compound semiconductorthat provides lattice matching with GaAs,

[0049] the second-conductive-type current diffusion layer is made of aGaP- or AlGaInP-based compound semiconductor, and

[0050] the second-conductive-type intermediate band gap layer is made ofan AlGaInP-based compound semiconductor.

[0051] With the semiconductor light-emitting device of this embodiment,ineffective currents can be reduced with a simple construction so thatan AlGaInP-based semiconductor light-emitting device of high emissionintensity can be realized.

[0052] In one embodiment of the present invention, thesecond-conductive-type intermediate band gap layer made of theAlGaInP-based compound semiconductor has a rate Δa/a of lattice matchingto GaAs falling within a range of −3.2%≦Δa/a≦−2.5%.

[0053] With the semiconductor light-emitting device of this embodiment,by the arrangement that the lattice matching rate Δa/a of thesecond-conductive-type intermediate band gap layer to GaAs is set towithin a range of −3.2%≦Δa/a≦−2.5% in an AlGaInP-based semiconductorlight-emitting device, ineffective currents can be reduced and theemission intensity can be enhanced, and besides, the operating voltagecan be lowered. Also, lattice defects on the device surface can belessened and the reliability can be improved.

[0054] In one embodiment of the present invention, thesecond-conductive-type intermediate band gap layer is composed of aplurality of AlGaInP layers having different rates of lattice matchingto GaAs, the lattice matching rates Δa/a of those AlGaInP layers eachfalling within a range of −3.2≦Δa/a≦−2.5%.

[0055] With the semiconductor light-emitting device of this embodiment,the AlGaInP layers composing the second-conductive-type intermediateband gap layer are different from one another in the lattice matchingrate and moreover the lattice matching rates Δa/a of those AlGaInPlayers each fall within a range of −3.2≦Δa/a≦−2.5%. As a result, in theAlGaInP-based light-emitting device, ineffective currents can bereduced, by which the emission intensity can be enhanced, and besidesthe operating voltage can further be lowered and lattice defects on thedevice surface can be lessened.

[0056] In one embodiment of the present invention, asecond-conductive-type protective layer made of GaP or an AlGaInP-basedcompound semiconductor having a Al composition ratio of not more than20% relative to the total of III group is stacked on thesecond-conductive-type intermediate band gap layer.

[0057] With the semiconductor light-emitting device of this embodiment,since GaP or an AlGaInP protective layer containing less Al is presenton the second-conductive-type intermediate band gap layer, there is noresistance layer with the second-conductive-type current diffusion layerformed on the AlGaInP protective layer, so that the operating voltagecan be lowered.

[0058] In one embodiment of the present invention, thesecond-conductive-type second cladding layer and thesecond-conductive-type third cladding layer both made of anAlGaInP-based compound semiconductor have a composition of(Al_(x)Ga_(1−x))_(0.5)In_(0.5)P (where 0.6≦X≦1.0).

[0059] With the semiconductor light-emitting device of this embodiment,the second-conductive-type second cladding layer and thesecond-conductive-type third cladding layer each have a composition of(Al_(x)Ga_(1−x))_(0.5)In_(0.5)P (where 0.6≦X≦1.0). As a result of this,the operating voltage can be lowered.

[0060] In one embodiment of the present invention, thesecond-conductive-type intermediate band gap layer has a layer thicknessof not more than 0.5 μm.

[0061] With the semiconductor light-emitting device of this embodiment,the second-conductive-type intermediate band gap layer has a layerthickness of not more than 0.5 μm. As a result of this, the operatingvoltage can be lowered.

[0062] In one embodiment of the present invention, thesecond-conductive-type intermediate band gap layer has a carrierconcentration of not less than 0.5×10¹⁸ cm⁻³.

[0063] With the semiconductor light-emitting device of this embodiment,the second-conductive-type intermediate band gap layer has a carrierconcentration of not less than 0.5×10¹⁸ cm⁻³. As a result of this, theoperating voltage can be lowered.

[0064] Also, there is provided a method for manufacturing asemiconductor light-emitting device, comprising the steps of:

[0065] stacking, one by one on one side of a surface of afirst-conductive-type semiconductor substrate, a first-conductive-typefirst cladding layer, a first-conductive-type or second-conductive-typeor an undoped active layer, a second-conductive-type second claddinglayer, a second-conductive-type intermediate band gap layer and asecond-conductive-type protective layer;

[0066] removing a device center region of the second-conductive-typeprotective layer and a device center region of thesecond-conductive-type intermediate band gap layer, respectively, byetching;

[0067] after the removal step of the second-conductive-type protectivelayer and intermediate band gap layer, stacking a current diffusionlayer on the second-conductive-type protective layer and thesecond-conductive-type second cladding layer to form, in thesecond-conductive-type current diffusion layer and thesecond-conductive-type second cladding layer, an energy band structurein which an upper-end position of valence band and a lower-end positionof conduction band are in a type II relation;

[0068] forming a first electrode overall on the other side of thesurface of the first-conductive-type semiconductor substrate; and

[0069] forming a second electrode over the device center region on thesecond-conductive-type current diffusion layer.

[0070] With this semiconductor light-emitting device manufacturingmethod, the removal region where the device center region of thesecond-conductive-type intermediate band gap layer has been removedbecomes high in resistance because an energy band structure in which theupper-end position of the valence band and the lower-end position of theconduction band are in the type II relation is formed in thesecond-conductive-type current diffusion layer and second cladding layerbecome high in resistance. Thus, the current flows to around the removalregion, so that ineffective currents flowing under the second electrodeformed in the device center region on the second-conductive-type currentdiffusion layer can be reduced, allowing the emission intensity to beenhanced. Therefore, a semiconductor light-emitting device of highemission intensity can be manufactured.

[0071] Also, there is provided a method for manufacturing asemiconductor light-emitting device, comprising the steps of:

[0072] stacking, one by one on one side of a surface of afirst-conductive-type semiconductor substrate, a first-conductive-typefirst cladding layer, a first-conductive-type or second-conductive-typeor an undoped active layer, a second-conductive-type second claddinglayer, a second-conductive-type intermediate band gap layer and asecond-conductive-type protective layer;

[0073] removing a device center region of the second-conductive-typeprotective layer and a device center region of thesecond-conductive-type intermediate band gap layer, respectively, byetching, and further removing an upper-side portion of a region of thesecond-conductive-type second cladding layer corresponding to theremoval region by etching;

[0074] after the removal step of the second-conductive-type protectivelayer, intermediate band gap layer and second cladding layer, stacking asecond-conductive-type current diffusion layer on thesecond-conductive-type protective layer and the second-conductive-typesecond cladding layer to form, in the second-conductive-type currentdiffusion layer and the second-conductive-type second cladding layer, anenergy band structure in which an upper-end position of valence band anda lower-end position of conduction band are in a type II relation;

[0075] forming a first electrode overall on the other side of thesurface of the first-conductive-type semiconductor substrate; and

[0076] forming a second electrode over the device center region on thesecond-conductive-type current diffusion layer.

[0077] With this semiconductor light-emitting device manufacturingmethod, the removal region where the device center region of thesecond-conductive-type intermediate band gap layer has been removedbecomes high in resistance because an energy band structure in which theupper-end position of the valence band and the lower-end position of theconduction band are in the type II relation is formed in thesecond-conductive-type current diffusion layer and second cladding layerbecome high in resistance. Thus, the current flows to around the removalregion, so that ineffective currents flowing under the second electrodeformed in the device center region on the second-conductive-type currentdiffusion layer can be reduced, allowing the emission intensity to beenhanced. Therefore, a semiconductor light-emitting device of highemission intensity can be manufactured.

[0078] Also, there is provided a method for manufacturing asemiconductor light-emitting device, comprising the steps of:

[0079] stacking, one by one on one side of a surface of afirst-conductive-type semiconductor substrate, a first-conductive-typefirst cladding layer, a first-conductive-type or second-conductive-typeor an undoped active layer, a second-conductive-type second claddinglayer, a second-conductive-type etching stop layer, asecond-conductive-type third cladding layer, a second-conductive-typeintermediate band gap layer and a second-conductive-type protectivelayer;

[0080] removing device center regions of the second-conductive-typeprotective layer, the second-conductive-type intermediate band gap layerand the second-conductive-type third cladding layer by etching;

[0081] after the removal step of the second-conductive-type protectivelayer, intermediate band gap layer and third cladding layer, stacking asecond-conductive-type current diffusion layer on thesecond-conductive-type protective layer and the second-conductive-typeetching stop layer to form, in the second-conductive-type currentdiffusion layer, the second-conductive-type etching stop layer and thesecond-conductive-type second cladding layer, an energy band structurein which an upper-end position of valence band and a lower-end positionof conduction band are in a type II relation;

[0082] forming a first electrode overall on the other side of thesurface of the first-conductive-type semiconductor substrate; and

[0083] forming a second electrode over the device center region on thesecond-conductive-type current diffusion layer.

[0084] With this semiconductor light-emitting device manufacturingmethod, the removal region where the device center region of thesecond-conductive-type intermediate band gap layer has been removedbecomes high in resistance because an energy band structure in which theupper-end position of the valence band and the lower-end position of theconduction band are in the type II relation is formed in thesecond-conductive-type current diffusion layer, thesecond-conductive-type eching stop layer and second cladding layerbecome high in resistance. Thus, the current flows to around the removalregion, so that ineffective currents flowing under the second electrodeformed in the device center region on the second-conductive-type currentdiffusion layer can be reduced, allowing the emission intensity to beenhanced. Therefore, a semiconductor light-emitting device of highemission intensity can be manufactured. Besides, the high-resistanceinterface can be formed with high controllability near the active layerby the presence of the second-conductive-type etching stop layer. Thus,the yield of this semiconductor light-emitting device can be improved.

[0085] Also, there is provided a method for manufacturing asemiconductor light-emitting device, comprising the steps of:

[0086] stacking, one by one on one side of a surface of afirst-conductive-type semiconductor substrate, a first-conductive-typefirst cladding layer, a first-conductive-type or second-conductive-typeor an undoped active layer, a second-conductive-type second claddinglayer, a second-conductive-type intermediate band gap layer and asecond-conductive-type protective layer;

[0087] removing regions of the second-conductive-type protective layerand the second-conductive-type intermediate band gap layer other thantheir device center regions, respectively, by etching;

[0088] after the removal step of the second-conductive-type protectivelayer and intermediate band gap layer, stacking a second-conductive-typecurrent diffusion layer on the second-conductive-type protective layerand the second-conductive-type second cladding layer to form, in thesecond-conductive-type current diffusion layer and thesecond-conductive-type second cladding layer, an energy band structurein which an upper-end position of valence band and a lower-end positionof conduction band are in a type II relation;

[0089] forming a first electrode overall on the other side of thesurface of the first-conductive-type semiconductor substrate; and

[0090] forming a second electrode over the region other than the devicecenter region on the second-conductive-type current diffusion layer.

[0091] With this semiconductor light-emitting device manufacturingmethod, the removal region where the region of thesecond-conductive-type intermediate band gap layer other than its devicecenter region has been removed becomes high in resistance due to thefact that an energy band structure in which the upper-end position ofthe valence band and the lower-end position of the conduction band arein the type II relation is formed in the second-conductive-type currentdiffusion layer and second cladding layer. Thus, the current flows toaround the device center region and, as a result, ineffective currentsflowing under the second electrode formed over the region other than thedevice center region on the second-conductive-type current diffusionlayer can be reduced, so that the emission intensity is enhanced.Therefore, a semiconductor light-emitting device of high emissionintensity can be manufactured.

[0092] Also, there is provided a method for manufacturing asemiconductor light-emitting device, comprising the steps of:

[0093] stacking, one by one on one side of a surface of afirst-conductive-type semiconductor substrate, a first-conductive-typefirst cladding layer, a first-conductive-type or second-conductive-typeor an undoped active layer, a second-conductive-type second claddinglayer, a second-conductive-type intermediate band gap layer and asecond-conductive-type protective layer;

[0094] removing regions of the second-conductive-type protective layerand the second-conductive-type intermediate band gap layer other thantheir device center regions, respectively, by etching, and furtherremoving an upper-side portion of a region of the second-conductive-typesecond cladding layer corresponding to the removal region by etching;

[0095] after the removal step of the second-conductive-type protectivelayer, intermediate band gap layer and second cladding layer, stacking asecond-conductive-type current diffusion layer on thesecond-conductive-type protective layer and the second-conductive-typesecond cladding layer to form, in the second-conductive-type currentdiffusion layer and the second-conductive-type second cladding layer, anenergy band structure in which an upper-end position of valence band anda lower-end position of conduction band are in a type II relation;

[0096] forming a first electrode overall on the other side of thesurface of the first-conductive-type semiconductor substrate; and

[0097] forming a second electrode over the region other than the devicecenter region on the second-conductive-type current diffusion layer.

[0098] With this semiconductor light-emitting device manufacturingmethod, the removal region where the region of thesecond-conductive-type intermediate band gap layer other than its devicecenter region has been removed becomes high in resistance due to thefact that an energy band structure in which the upper-end position ofthe valence band and the lower-end position of the conduction band arein the type II relation is formed in the second-conductive-type currentdiffusion layer and second cladding layer. Thus, the current flows toaround the device center region and, as a result, ineffective currentsflowing under the second electrode formed over the region other than thedevice center region on the second-conductive-type current diffusionlayer can be reduced, so that the emission intensity is enhanced.Therefore, a semiconductor light-emitting device of high emissionintensity can be manufactured.

[0099] Also, there is provided a method for manufacturing asemiconductor light-emitting device, comprising the steps of:

[0100] stacking, one by one on one side of a surface of afirst-conductive-type semiconductor substrate, a first-conductive-typefirst cladding layer, a first-conductive-type or second-conductive-typeor an undoped active layer, a second-conductive-type second claddinglayer, a second-conductive-type etching stop layer, asecond-conductive-type third cladding layer, a second-conductive-typeintermediate band gap layer and a second-conductive-type protectivelayer;

[0101] removing regions of the second-conductive-type protective layer,the second-conductive-type intermediate band gap layer and thesecond-conductive-type third cladding layer other than their devicecenter regions, respectively, by etching;

[0102] after the removal step of the second-conductive-type protectivelayer, intermediate band gap layer and third cladding layer, stacking asecond-conductive-type current diffusion layer on thesecond-conductive-type protective layer and the second-conductive-typeetching stop layer to form, in the second-conductive-type currentdiffusion layer, the second-conductive-type etching stop layer and thesecond-conductive-type second cladding layer, an energy band structurein which an upper-end position of valence band and a lower-end positionof conduction band are in a type II relation;

[0103] forming a first electrode overall on the other side of thesurface of the first-conductive-type semiconductor substrate; and

[0104] forming a second electrode over the region other than the devicecenter region on the second-conductive-type current diffusion layer.

[0105] With this semiconductor light-emitting device manufacturingmethod, the removal region where the region of thesecond-conductive-type intermediate band gap layer other than its devicecenter region has been removed becomes high in resistance due to thefact that an energy band structure in which the upper-end position ofthe valence band and the lower-end position of the conduction band arein the type II relation is formed in the second-conductive-type currentdiffusion layer, the second-conductive-type eching stop layer and secondcladding layer. Thus, the current flows to around the device centerregion and, as a result, ineffective currents flowing under the secondelectrode formed over the region other than the device center region onthe second-conductive-type current diffusion layer can be reduced, sothat the emission intensity is enhanced. Therefore, a semiconductorlight-emitting device of high emission intensity can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

[0106] The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

[0107]FIG. 1A is a top view of a semiconductor light-emitting devicewhich is a first embodiment of the invention, FIG. 1B is a sectionalview of the semiconductor light-emitting device, and FIG. 1C is afunctional view showing a current flow in the semiconductorlight-emitting device;

[0108]FIGS. 2A to 2C are band junction diagrams for explaining theeffects of the invention;

[0109]FIG. 3A is a top view of a semiconductor light-emitting devicewhich is a second embodiment of the invention, FIG. 3B is a sectionalview of the semiconductor light-emitting device, and FIG. 3C is afunctional view showing a current flow in the semiconductorlight-emitting device;

[0110]FIG. 4A is a top view of a semiconductor light-emitting devicewhich is a third embodiment of the invention, FIG. 4B is a sectionalview of the semiconductor light-emitting device, and FIG. 4C is afunctional view showing a current flow in the semiconductorlight-emitting device;

[0111]FIG. 5A is a top view of a semiconductor light-emitting devicewhich is a fourth embodiment of the invention, FIG. 5B is a sectionalview of the semiconductor light-emitting device, and FIG. 5C is afunctional view showing a current flow in the semiconductorlight-emitting device;

[0112]FIG. 6A is a top view of a semiconductor light-emitting devicewhich is a fifth embodiment of the invention, FIG. 6B is a sectionalview of the semiconductor light-emitting device, and FIG. 6C is afunctional view showing a current flow in the semiconductorlight-emitting device;

[0113]FIG. 7A is a top view of a semiconductor light-emitting devicewhich is a sixth embodiment of the invention, FIG. 7B is a sectionalview of the semiconductor light-emitting device, and FIG. 7C is afunctional view showing a current flow in the semiconductorlight-emitting device;

[0114]FIG. 8A is a top view of a semiconductor light-emitting devicewhich is a seventh embodiment of the invention, and FIG. 8B is asectional view of the semiconductor light-emitting device;

[0115]FIG. 9A is a top view of a semiconductor light-emitting devicewhich is an eighth embodiment of the invention, FIG. 9B is a sectionalview of the semiconductor light-emitting device, and FIG. 9C is afunctional view showing a current flow in the semiconductorlight-emitting device;

[0116]FIG. 10 is a chart showing variations in emission intensity versusthe difference in diameter between electrode and current blocking(removal) region in the semiconductor light-emitting device;

[0117]FIG. 11 is a chart showing the relationship between mismatch ofthe intermediate band gap layer and operating voltage in thesemiconductor light-emitting device;

[0118]FIG. 12 is a chart showing the relationship between mismatch ofthe intermediate band gap layer and the number of lattice defects in thesemiconductor light-emitting device;

[0119]FIG. 13A is a top view of a semiconductor light-emitting devicewhich is a ninth embodiment of the invention, and FIG. 13B is asectional view of the semiconductor light-emitting device;

[0120]FIG. 14 is a band junction diagram for explaining the effects ofthe semiconductor light-emitting device;

[0121]FIG. 15 is a chart showing the relationship between Al compositionratio of a protective layer and operating voltage in a semiconductorlight-emitting device which is a tenth embodiment of the invention;

[0122]FIG. 16 is a chart showing the relationship between Al compositionratio of a p-cladding layer and operating voltage in a semiconductorlight-emitting device which is an eleventh embodiment of the invention;

[0123]FIG. 17 is a chart showing the relationship between layerthickness of the intermediate band gap layer and operating voltage inthe semiconductor light-emitting device;

[0124]FIG. 18 is a chart showing the relationship between carrierconcentration of the intermediate band gap layer and operating voltagein the semiconductor light-emitting device;

[0125] FIGS. 19A-19D are views showing a semiconductor light-emittingdevice manufacturing method which is a twelfth embodiment of theinvention;

[0126] FIGS. 20A-20D are views showing a semiconductor light-emittingdevice manufacturing method which is a thirteenth embodiment of theinvention;

[0127] FIGS. 21A-21D are views showing a semiconductor light-emittingdevice manufacturing method which is a fourteenth embodiment of theinvention;

[0128] FIGS. 22A-22D are views showing a semiconductor light-emittingdevice manufacturing method which is a fifteenth embodiment of theinvention;

[0129] FIGS. 23A-23D are views showing a semiconductor light-emittingdevice manufacturing method which is a sixteenth embodiment of theinvention;

[0130] FIGS. 24A-24D are views showing a semiconductor light-emittingdevice manufacturing method which is a seventeenth embodiment of theinvention;

[0131]FIG. 25A is a top view of a semiconductor light-emitting deviceaccording to the prior art, FIG. 25B is a sectional view of thesemiconductor light-emitting device, and FIG. 25C is a functional viewshowing a current flow in the semiconductor light-emitting device;

[0132]FIG. 26A is a top view of another semiconductor light-emittingdevice according to the prior art, FIG. 26B is a sectional view of thesemiconductor light-emitting device, and FIG. 26C is a functional viewshowing a current flow in the semiconductor light-emitting device; and

[0133]FIG. 27A is a top view of still another semiconductorlight-emitting device according to the prior art, FIG. 27B is asectional view of the semiconductor light-emitting device, and FIG. 27Cis a functional view showing a current flow in the semiconductorlight-emitting device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0134] Hereinbelow, the semiconductor light-emitting device and methodof manufacture thereof according to the present invention are describedin detail by way of embodiments thereof illustrated in the accompanyingdrawings.

First Embodiment

[0135]FIGS. 1A, 1B and 1C are a top view, a sectional view, and afunctional view showing a current flow, respectively, of a semiconductorlight-emitting device which is a first embodiment of the invention.

[0136] In this semiconductor light-emitting device, as shown in FIG. 1B,an n-GaAs buffer layer 1 (thickness: 0.5 μm, Si doping: 5×10¹⁷ cm⁻³), ann-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first cladding layer 2 (thickness:1.0 μm, Si doping: 5×10¹⁷ cm⁻³), an undoped(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 3 (thickness: 0.6 μm), ap-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 4 (thickness:0.7 μm, Zn doping: 5×10¹⁷ cm⁻³), a p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)Pintermediate band gap layer 5 (thickness: 0.15 μm, Zn doping: 2×10 ¹⁸cm⁻³), and a p-GaP current diffusion layer 6 (thickness: 6 μm, Zndoping: 2×10¹⁸ cm⁻³) are stacked one by one on an n-GaAs substrate 10 byMOCVD process.

[0137] In this case, a device center region of the p-AlGaInPintermediate band gap layer 5 is removed in a circular shape (thediameter of this circular-shaped removal region is 100 μm). Then, afirst electrode 11 is formed on the substrate side while acircular-shaped second electrode 12 having a diameter of 100 μm isformed on the grown layer side (shown in FIG. 1A). It is noted that thep-AlGaInP intermediate band gap layer 5 has a Δa/a=−2.8% mismatch inlattice matching ratio with respect to the n-GaAs substrate 10.

[0138] In this semiconductor light-emitting device, as shown in FIG. 1C,a current injected from the grown-layer side second electrode 12 avoidsthe region at which the p-AlGaInP intermediate band gap layer 5 providedunder the second electrode 12 has been removed (removal region), flowingto around the removal region. Thus, light emission occurs over a regionof the active layer 3 corresponding to the region other than the removalregion (under the second electrode 12). The reason of this is describedbelow.

[0139] The p-AlGaInP second cladding layer 4 and the p-GaP currentdiffusion layer 6 are so positioned as to have such a positionalrelation of their conduction band lower ends and the valence band upperends with respect to the vacuum level as shown in FIG. 2A. When aheterojunction is formed in this case, there results a junction state ofso-called type-II energy band structure which involves an increased banddiscontinuity of valence band.

[0140] Therefore, as an interface between the p-AlGaInP second claddinglayer 4 and the p-GaP current diffusion layer 6 is present in theremoval region under the second electrode 12, the band junction state atthe interface is as shown in FIG. 2B, where the notch of the valenceband at the junction becomes large, causing a high resistance, to thecurrent (holes) injected from the second electrode 12 on the grown layerside (where the notch height is about 0.28 eV).

[0141] Meanwhile, in the region other than the removal region (under thesecond electrode 12), the layer structure is given by the p-AlGaInPsecond cladding layer 4, the p-AlGaInP intermediate band gap layer 5 andthe p-GaP current diffusion layer 6, where the band junction state is asshown in FIG. 2C due to the presence of the p-AlGaInP intermediate bandgap layer 5. In this case, the band discontinuity is divided with theresults of smaller notch of valence band at the junction, causing a lowresistance (where the notch is divided into 0.15 eV and 0.13 eV).

[0142] Under operation as a device, in the case of a device made up onlyof the interface between the p-AlGaInP second cladding layer 4 and thep-GaP current diffusion layer 6, as in the removal region under thesecond electrode 12, the voltage at a 20 mA conduction is about 3.5 Vbecause of a large notch height. Meanwhile, in the case of asemiconductor light-emitting device having the pAlGaInP intermediateband gap layer 5 device, as in the region other than the removal region(under the second electrode 12), the voltage at a 20 mA conduction isabout 2.1 V, hence a voltage difference being as much as 1.4 V.

[0143] As a result, at a 20 mA conduction, as shown in FIG. 1C, acurrent injected from the grown-layer side second electrode 12 avoidsthe removal region under the second electrode 12, flowing to around theregion, causing light emission to occur over a region of the activelayer 3 corresponding to the region other than the removal region (underthe second electrode 12).

[0144] In the case of this semiconductor light-emitting device, as inthe semiconductor light-emitting device shown in FIG. 26, there occursno sneak current to under the current blocking layer, so thatineffective currents are almost completely eliminated, resulting inincreased emission intensity.

[0145] When this semiconductor light-emitting device of the firstembodiment was applied to a 5 mm dia. molded article, the emissionintensity at a 20 mA conduction was 3.0 cd, 1.5 times higher than thatof the semiconductor light-emitting device shown in FIG. 26.

Second Embodiment

[0146]FIGS. 3A, 3B and 3C are a top view, a sectional view and afunctional view, respectively, of a semiconductor light-emitting devicewhich is a second embodiment of the invention.

[0147] In this semiconductor light-emitting device, as shown in FIG. 3B,an n-GaAs buffer layer 21 (thickness: 0.5 μm, Si doping: 5×10¹⁷ cm⁻³),an n-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first cladding layer 22(thickness: 1.0 μm, Si doping: 5×10¹⁷ cm⁻³) an undoped(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 23 (thickness: 0.6 μm), ap-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 24 (thickness:0.7 μm, Zn doping: 5×10¹⁷ cm⁻³), a p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)Pintermediate band gap layer 25 (thickness: 0.15 μm, Zn doping: 2×10¹⁸cm⁻³), and a p-GaP current diffusion layer 26 (thickness: 6 μm, Zndoping: 2×10¹⁸ cm⁻³) are stacked one by one on an n-GaAs substrate 30 byMOCVD process.

[0148] In this case, a device center region of the p-AlGaInPintermediate band gap layer 25 is removed in a circular shape, and aregion of the p-AlGaInP second cladding layer 24 corresponding to theremoval region is removed halfway on the upper side (remainingthickness: 0.3 μm) (the diameter of this circular shape is 100 μm).Then, a first electrode 31 is formed on the substrate side while acircular-shaped second electrode 32 having a diameter of 100 μm isformed on the grown layer side.

[0149] In this semiconductor light-emitting device, according to thesame principle as in the semiconductor light-emitting device of thefirst embodiment, as shown in FIG. 3C, a current injected from thegrown-layer side second electrode 32 avoids the removal region under thesecond electrode 32, flowing to around the removal region. Thus, lightemission occurs over a region of the active layer 23 corresponding tothe region other than the removal region (under the second electrode32).

[0150] In the case of this semiconductor light-emitting device, ascompared with the semiconductor light-emitting device of the firstembodiment, the high-resistance interface formed by the p-AlGaInP secondcladding layer 24 and the p-GaP current diffusion layer 26 under thesecond electrode 32 is just above the active layer 23 as near as 0.3 μmthereto, so that ineffective currents are lessened, resulting in furtherincreased emission intensity.

[0151] When this semiconductor light-emitting device of the secondembodiment was applied to a 5 mm dia. molded article, the emissionintensity at a 20 mA conduction (operating voltage: 2.1 V) was 3.3 cd,showing a 10% increase as compared with the semiconductor light-emittingdevice of the first embodiment.

Third Embodiment

[0152]FIGS. 4A, 4B and 4C are a top view, a sectional view and afunctional view, respectively, of a semiconductor light-emitting devicewhich is a third embodiment of the invention. In this semiconductorlight-emitting device, as shown in FIGS. 4A and 4B, an n-GaAs bufferlayer 41 (thickness: 0.5 μm, Si doping: 5×10¹⁷ cm⁻³), ann-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first cladding layer 42 (thickness:1.0 μm, Si doping: 5×10¹⁷ cm⁻³), an undoped(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 43 (thickness: 0.6 μm), ap-(A1 _(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 44(thickness: 0.3 μm), a p-GaInP etching stop layer 45 (thickness: 0.01μm, Zn doping: 5×10¹⁷ cm⁻³), a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P thirdcladding layer 46 (thickness: 0.4 μm, Zn doping: 5×10¹⁷ cm⁻³), ap-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)P intermediate band gap layer 47(thickness: 0.15 μm, Zn doping: 2×10 ¹⁸ cm⁻³), and a p-GaP currentdiffusion layer 48 (thickness: 6 μm, Zn doping: 2×10¹⁸ cm⁻³) are stackedone by one on an n-GaAs substrate 50 by MOCVD process.

[0153] In this case, device center regions of the p-AlGaInP intermediateband gap layer 47 and the p-AlGaInP third cladding layer 46 are removedin a circular shape (the diameter of these circular-shaped removalregions is 100 μm) Then, a first electrode 51 is formed on the substrateside while a circular-shaped second electrode 52 having a diameter of100 μm is formed on the grown layer side.

[0154] In this semiconductor light-emitting device also, as shown inFIG. 4C, a current injected from the grown-layer side second electrode52 avoids the removal region under the second electrode 52, flowing toaround the removal region. Thus, light emission occurs over a region ofthe active layer 43 corresponding to the region other than the removalregion (under the second electrode 52).

[0155] As to the reason of this, also at the interface between thep-GaInP etching stop layer 45 and the p-GaP current diffusion layer 48present in the etched region under the second electrode 52, the bandjunction state is one similar to FIG. 2B, where the notch at thejunction becomes large, causing a high resistance, to the current(holes) injected from the second electrode 52 on the grown layer side(where the notch height is about 0.26 eV and the voltage at a 20 mAconduction is as large as 3.3 V).

[0156] This semiconductor light-emitting device of the third embodimenthas effects similar to those of the semiconductor light-emitting deviceof the second embodiment, and further has better controllability informing, at a position 0.3 μm just above the active layer 43, thehigh-resistance interface formed by the p-AlGaInP second cladding layer44 and the p-GaP current diffusion layer 48 under the second electrode52, as compared with the semiconductor light-emitting device of thesecond embodiment, by virtue of the use of the p-GaInP etching stoplayer 45. Thus, the yield of this semiconductor light-emitting device isimproved.

[0157] With this semiconductor light-emitting device of the thirdembodiment, the emission intensity at a 20 mA conduction (operatingvoltage: 2.1 V) was 3.3 cd, the same as in the semiconductorlight-emitting device of the second embodiment, while the yield wasimproved to 99% in contrast to 75% of the second embodiment.

Fourth Embodiment

[0158]FIGS. 5A, 5B and 5C are a top view, a sectional view and afunctional view, respectively, of a semiconductor light-emitting devicewhich is a fourth embodiment of the invention.

[0159] In this semiconductor light-emitting device, as shown in FIGS. 5Aand 5B, an n-GaAs buffer layer 61 (thickness: 0.5 μm, Si doping: 5×10¹⁷cm⁻³), a DBR (optical reflection) layer 62 formed of ten pairs ofn-Al_(0.5)In_(0.5)P layer and n-(Al_(0.4)Ga_(0.6))_(0.5)In_(0.5)P layer(each one layer's thickness: 0.05 μm, Si doping: 5×10¹⁷ cm⁻³), ann-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first cladding layer 63 (thickness:1.0 μm, Si doping: 5×10¹⁷ cm⁻³), a p-(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)Pactive layer 64 (thickness: 0.6 μm, Zn doping: 2×10¹⁷ cm⁻³), ap-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 65 (thickness:0.7 μm Zn doping: 5×10¹⁷ cm⁻³), a p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)Pintermediate band gap layer 66 (thickness: 0.15 μm, Zn doping: 2×10 ¹⁸cm⁻³), and a p-(Al_(0.05)Ga_(0.95))_(09.)In_(0.1)P current diffusionlayer 67 (thickness: 6 μm, Zn doping: 3×10¹⁸ cm⁻³) are stacked one byone on an n-GaAs substrate 70 by MOCVD process.

[0160] In this case, peripheries of the p-AlGaInP intermediate band gaplayer 66 are removed with its device center region left in a circularshape (the diameter of this circular shape is 100 μm). Then, a firstelectrode 71 is formed on the substrate side while a second electrode 72is formed on the grown layer side over a region other than a 100 μm dia.circular-shaped region which is left as it is.

[0161] A heterojunction of type II is formed also between thep-(Al_(0.05)Ga_(0.95))_(0.9)In_(0.1)P current diffusion layer 67 and thep-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 65, and ahigh-resistance interface is formed at the removal region of theintermediate band gap layer 66.

[0162] In the case of this semiconductor light-emitting device, as shownin FIG. 5C, a current injected from the grown-layer side secondelectrode 72 avoids the removal region under the second electrode 72,flowing to the device center region. Thus, light emission occurs over aregion of the active layer 64 corresponding to the region other than theremoval region (under the second electrode 72).

[0163] As a structure to be compared with this semiconductorlight-emitting device, there has been a semiconductor light-emittingdevice having a structure shown in FIGS. 27A-27C similar to theprior-art semiconductor light-emitting device shown in FIG. 26. In thissemiconductor light-emitting device shown in FIGS. 27A-27C, as in thesemiconductor light-emitting device shown in FIG. 26, most part of thecurrent sneaks to under the second electrode on the under side of thecurrent blocking layer, resulting in ineffective current, with lowerlight intensity (4 cd at a 20 mA conduction with a radiation angle of±2°). As compared with this semiconductor light-emitting device shown inFIGS. 27A-27C, the semiconductor light-emitting device of this fourthembodiment involves less sneak current going to under the removalregion, so that ineffective currents are almost completely eliminated,resulting in increased emission intensity.

[0164] With this semiconductor light-emitting device of the fourthembodiment, the emission intensity at a 20 mA conduction was 6.0 cd, 1.5times higher than that of the semiconductor light-emitting device shownin FIG. 27, where the operating voltage was 2.35 V (because of a smallcurrent injection area, the operating voltage is larger than in thesemiconductor light-emitting device shown in FIG. 25).

Fifth Embodiment

[0165]FIGS. 6A, 6B and 6C are a top view, a sectional view and afunctional view, respectively, of a semiconductor light-emitting devicewhich is a fifth embodiment of the invention.

[0166] In this semiconductor light-emitting device, as shown in FIGS. 6Aand 6B, an n-GaAs buffer layer 81 (thickness: 0.5 μm, Si doping:5×10^(17 cm) ⁻³), a DBR (optical reflection) layer 82 formed of tenpairs of n-Al_(0.5)In_(0.5)P layer andn-(Al_(0.4)Ga_(0.6))_(0.5)In_(0.5)P layer (each one layer's thickness:0.05 μm, Si doping: 5×10¹⁷ cm⁻³), an n-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)Pfirst cladding layer 83 (thickness: 1.0 μm, Si doping: 5×10¹⁷ cm-³), ap-(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 84 (thickness: 0.6 μm,Zn doping: 2×10¹⁷ cm⁻³), a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P secondcladding layer 85 (thickness: 0.7 μm, Zn doping: 5×10¹⁷ cm⁻³), ap-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)P intermediate band gap layer 86(thickness: 0.15 μm, Zn doping: 2×10¹⁸ cm⁻³), and ap-(Al_(0.05)Ga_(0.95))_(0.9)In_(0.1)P current diffusion layer 87(thickness: 6 μm, Zn doping: 3×10¹⁸ cm⁻³) are stacked one by one on ann-GaAs substrate 90 by MOCVD process.

[0167] In this case, peripheries of the p-AlGaInP intermediate band gaplayer 86 are removed with its device center region left in a circularshape, and a region of the p-AlGaInP second cladding layer 85corresponding to the removal region is removed halfway on the upper side(remaining thickness: 0.3 μm) (the diameter of this circular shape is100 μm). Then, a first electrode 91 is formed on the substrate sidewhile a second electrode 92 is formed on the grown layer side over aregion other than a 100 μm dia. circular-shaped region which is left asit is.

[0168] In the case of this semiconductor light-emitting device, as shownin FIG. 6C, a current injected from the grown-layer side secondelectrode 92 avoids the removal region under the second electrode 92,flowing to the device center region. Thus, light emission occurs over aregion of the active layer 84 corresponding to the region other than theremoval region (under the second electrode 92).

[0169] This semiconductor light-emitting device of the fifth embodimenthas effects similar to those of the semiconductor light-emitting deviceof the fourth embodiment, and further, as compared with thesemiconductor light-emitting device of the fourth embodiment, thehigh-resistance interface formed by the p-AlGaInP second cladding layer85 and the p-AlGaInP current diffusion layer 87 under the secondelectrode 92 is just above the active layer 84 as near as 0.3 μmthereto, so that ineffective currents are lessened, resulting in furtherincreased emission intensity. The emission intensity at a 20 mAconduction (operating voltage: 2.35 V) was 6.6 cd, showing a 10%increase as compared with the semiconductor light-emitting device of thefirst embodiment.

Sixth Embodiment

[0170]FIGS. 7A, 7B and 7C are a top view, a sectional view and afunctional view, respectively, of a semiconductor light-emitting devicewhich is a sixth embodiment of the invention.

[0171] In this semiconductor light-emitting device, as shown in FIGS. 7Aand 7B, an n-GaAs buffer layer 101 (thickness: 0.5 μm, Si doping: 5×10¹⁷cm⁻³), a DBR (optical reflection) layer 102 formed of ten pairs ofn-Al_(0.5)In_(0.5)P layer and n-(Al_(0.4)Ga_(0.6))_(0.5)In_(0.5)P layer(each one layer's thickness: 0.05 μm, Si doping: 5×10¹⁷ cm⁻³), ann-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first cladding layer 103 (thickness:1.0 μm, Si doping: 5×10¹⁷ cm⁻³), a p-(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)Pactive layer 104 (thickness: 0.6 μm, Zn doping: 2×10¹⁷ cm⁻³), ap-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 105(thickness: 0.3, Zn doping: 5×10¹⁷ cm⁻³), a p-Ga_(0.5)In_(0.5)P etchingstop layer 106 (thickness: 0.01 μm, Zn doping: 5×10¹⁷ cm⁻³), ap-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P third cladding layer 107 (thickness:0.4 μm, Zn doping: 5×10¹⁷ cm⁻³) a p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)Pintermediate band gap layer 108 (thickness: 0.15 μm, Zn doping: 2×10¹⁸cm⁻³), and a p-(Al_(0.05)Ga_(0.95))_(0.9)In_(0.1)P current diffusionlayer 109 (thickness: 6 μm, Zn doping: 3×10¹⁸ cm⁻³) are stacked one byone on an n-GaAs substrate 110 by MOCVD process.

[0172] In this case, peripheries of the p-AlGaInP intermediate band gaplayer 108 are removed with its device center region left in a circularshape, and a region of the p-AlGaInP third cladding layer 107corresponding to the removal region is removed (the diameter of thiscircular shape is 100 μm). Then, a first electrode 111 is formed on thesubstrate side while a second electrode 112 is formed on the grown layerside over a region other than a 100 μm dia. circular-shaped region whichis left as it is.

[0173] In the case of this semiconductor light-emitting device, as shownin FIG. 7C, a current injected from the grown-layer side secondelectrode 112 avoids the removal region under the second electrode 112,flowing to the device center region. Thus, light emission occurs over aregion of the active layer 104 corresponding to the region other thanthe removal region (under the second electrode 112).

[0174] This semiconductor light-emitting device of the sixth embodimenthas effects similar to those of the semiconductor light-emitting deviceof the fifth embodiment, and further, has better controllability informing, at a position 0.3 μm just above the active layer 104, thehigh-resistance interface formed by the p-AlGaInP third cladding layer107 and the p-AlGaInP current diffusion layer 109 under the secondelectrode 112, as compared with the semiconductor light-emitting deviceof the fifth embodiment, by virtue of the use of the etching stop layer106. Thus, the yield of this semiconductor light-emitting device isimproved.

[0175] With this semiconductor light-emitting device of the sixthembodiment, the emission intensity at a 20 mA conduction (operatingvoltage: 2.35 V) was 6.6 cd, the same as in the semiconductorlight-emitting device of the fifth embodiment, while the yield wasimproved to 99% (against 75% of the semiconductor light-emitting deviceof the fifth embodiment).

Seventh Embodiment

[0176]FIGS. 8A and 8B are a top view and a sectional view, respectively,of a semiconductor light-emitting device which is a seventh embodimentof the invention.

[0177] In this semiconductor light-emitting device, as shown in FIGS. 8Aand 8B, an n-GaAs buffer layer 121 (thickness: 0.5 μm, Si doping: 5×10¹⁷cm⁻³), an n-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first cladding layer 122(thickness: 1.0 μm, Si doping: 5×10¹⁷ cm⁻³) an undoped(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 123 (thickness: 0.6 μm),a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 124(thickness: 0.7 μm, Zn doping: 5×10¹⁷ cm⁻³), ap-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)P intermediate band gap layer 125(thickness: 0.15 μm, Zn doping: 2×10¹⁸ cm⁻³), a p-GaP protective layer126 (thickness: 0.1 μm, Zn doping: 1×10¹⁸ cm⁻³), and a p-GaP currentdiffusion layer 127 (thickness: 6 μm, Zn doping: 2×10¹⁸ cm⁻³) arestacked one by one on an n-GaAs substrate 130 by MOCVD process.

[0178] In this case, device center regions of the p-GaP protective layer126 and the p-AlGaInP intermediate band gap layer 125 are removed in acircular shape (the diameter of these circular-shaped removal regions is100 μm). Then, a first electrode 131 is formed on the substrate sidewhile a second electrode 132 having a diameter of 100 μm is formed onthe grown layer side over a region opposite to the removal region (shownin FIG. 8A).

[0179] This semiconductor light-emitting device of the seventhembodiment differs from the semiconductor light-emitting device of thefirst embodiment shown in FIG. 1 in that the p-GaP protective layer 126is present on the p-AlGaInP intermediate band gap layer 125.

[0180] In the case of this semiconductor light-emitting device, acurrent injected from the grown-layer side second electrode 132 avoidsthe regions at which the p-GaP protective layer 126 and the p-AlGaInPintermediate band gap layer 125 provided under the second electrode 132have been removed, flowing to around the removal region. Thus, lightemission occurs over a region of the active layer 123 corresponding tothe region other than the removal region (under the second electrode132).

[0181] With this semiconductor light-emitting device, the operatingvoltage at 20 mA was 2.0 V, which was a decrease of 0.1 V as comparedwith the semiconductor light-emitting device of the first embodiment.This is because whereas the ground of the regrown interface in theregion through which the current flows in the case of the semiconductorlight-emitting device of the first embodiment is given by the p-AlGaInPintermediate band gap layer 125, which is a layer containing much Al(36% on the basis of a total of III group), the counterpart in the caseof this semiconductor light-emitting device of the seventh embodiment isgiven by the p-GaP protective layer 126, which is a layer containing noAl, so that there occurs no resistive layer due to any Al oxide at theinterface.

[0182] When this semiconductor light-emitting device of the seventhembodiment was applied to a 5 mm dia. molded article, the emissionintensity at a 20 mA conduction was 3.0 cd, the same as in thesemiconductor light-emitting device of the first embodiment.

Eighth Embodiment

[0183]FIGS. 9A, 9B and 9C are a top view, a sectional view and afunctional view, respectively, of a semiconductor light-emitting devicewhich is an eighth embodiment of the invention.

[0184] In this semiconductor light-emitting device, as shown in FIGS. 9Aand 9B, an n-GaAs buffer layer 141 (thickness: 0.5 μm, Si doping: 5×10¹⁷cm⁻³), an n-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first cladding layer 142(thickness: 1.0 μm, Si doping: 5×10¹⁷ cm⁻³), an undoped(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 143 (thickness: 0.6 μm),a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 144(thickness: 0.7, Zn doping: 5×10¹⁷ cm⁻³), ap-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)P intermediate band gap layer 145(thickness: 0.15 μm, Zn doping: 2×10¹⁸ cm⁻³), a p-GaP protective layer146 (thickness: 0.1 μm, Zn doping: 1×10¹⁸ cm⁻³), and a p-GaP currentdiffusion layer 147 (thickness: 6 μm, Zn doping: 2×10¹⁸ cm⁻³) arestacked one by one on an n-GaAs substrate 150 by MOCVD process.

[0185] In this case, device center regions of the p-GaP protective layer146 and the p-AlGaInP intermediate band gap layer 145 are removed in acircular shape (the diameter of these circular-shaped removal regions153 is 100 μm) Then, a first electrode 151 is formed on the substrateside while a second electrode 152 is formed on the grown layer side overa region opposite to the removal region.

[0186] This semiconductor light-emitting device of the eighth embodimenthas a 80 μm diameter of the grown-layer side second electrode 152, 20 μmsmaller than that of the semiconductor light-emitting device of theseventh embodiment shown in FIG. 8 (the electrode diameter in the firstembodiment is 100 μm).

[0187] In the case of this semiconductor light-emitting device, as shownin FIG. 9C, a current injected from the grown-layer side secondelectrode 152 avoids the removal region present under the secondelectrode 152, flowing to around the removal region. Thus, lightemission occurs over a region of the active layer 143 corresponding tothe region other than the removal region (under the second electrode152). However, since there is a positional shift of 10 μm between theend of the second electrode 152 and the end of the removal region(center region), the current spreading becomes slightly worse than inthe seventh embodiment (in which the electrode end and the removalregion end are coincident).

[0188] With this semiconductor light-emitting device of the eighthembodiment, the emission intensity at a 20 mA conduction was 2.7 cd,which is 90% that of the semiconductor light-emitting device shown inthe seventh embodiment shown in FIG. 8.

[0189]FIG. 10 shows the relationship of the light intensity of theeighth embodiment device to the difference between electrode diameter(the diameter of the second electrode 152) and current blocking regiondiameter (the diameter of the removal region). In FIG. 10, the minussign represents that the electrode diameter is smaller than the currentblocking region diameter, and the plus sign represents that it islarger, conversely.

[0190] As can be understood from FIG. 10, in the case where theelectrode diameter is larger than the current blocking region diameterconverse to the semiconductor light-emitting device of the eighthembodiment, there is formed a light emitting region under the electrode,causing the light intensity to become smaller.

[0191] If the difference between the electrode diameter and the currentblocking region diameter is within ±40 μm, then the resulting lightintensity is 80% or more that in the case where the two diameters areequal to each other.

[0192] Also, FIG. 11 shows the 20 mA operating voltage of the eighthembodiment resulting when the mismatch (in composition) of theintermediate band gap layer 145 is varied. The operating voltageincreases as the mismatch becomes smaller than −2.8% (meaning that thecomposition approaches GaP). This is because, with reference to the bandjunction diagram shown by FIG. 2C, the notch of the valence band at theinterface of the p-AlGaInP cladding layer and the p-AlGaInP intermediatelayer increases. Desirably, the mismatch of the intermediate band gap isnot less than −3.2% in order that the operating voltage is not more than2.5 V, which is practically free from any problems.

[0193] Also, FIG. 12 shows the number of defects (per mm²) at thecrystal surface of the first embodiment resulting when the mismatch (incomposition) of the intermediate band gap layer is varied. The crystaldefects increase as the mismatch becomes larger than −2.8% (meaning thatthe In composition increases). This is because, at a mismatched layersuch as the intermediate layer, In hardly migrates but tends toanisotropically grow because of some stress. Desirably, the mismatch ofthe intermediate band gap is not more than −2.5% in order that thenumber of defects is not more than 20, which is practically free fromany problems.

Ninth Embodiment

[0194]FIGS. 13A and 13B are a top view and a sectional view,respectively, of a semiconductor light-emitting device which is a ninthembodiment of the invention.

[0195] In this semiconductor light-emitting device, as shown in FIGS.13A and 13B, an n-GaAs buffer layer 161 (thickness: 0.5 μm, Si doping:5×10¹⁷ cm⁻³), an n-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first claddinglayer 162 (thickness: 1.0 μm, Si doping: 5×10¹⁷ cm⁻³), an undoped(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 163 (thickness: 0.6 μm),a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 164(thickness: 0.7 μm, Zn doping: 5×10¹⁷ cm⁻³), a p-AlGaInP intermediateband gap layer 165 (thickness: 0.15 μm, Zn doping: 2×10¹⁸ cm⁻³), a p-GaPprotective layer 166 (thickness: 0.1 μm, Zn doping: 1×10¹⁸ cm⁻³), and ap-GaP current diffusion layer 167 (thickness: 6 μm, Zn doping: 2×10¹⁸cm⁻³) are stacked one by one on an n-GaAs substrate 170 by MOCVDprocess.

[0196] In this case, device center regions of the p-GaP protective layer166 and the p-AlGaInP intermediate band gap layer 165 are removed in acircular shape (the diameter of these circular-shaped removal regions is100 μmim). Then, a first electrode 171 is formed on the substrate sidewhile a second electrode 172 having a diameter of 100 μm is formed onthe grown layer side over a region opposite to the removal region.

[0197] This semiconductor light-emitting device of the ninth embodimentdiffers from the semiconductor light-emitting device of the seventhembodiment shown in FIG. 8 in that the intermediate band gap layer 165is formed of three layers. More specifically, the intermediate band gaplayer 165 is formed of a first intermediate band gap layer 165A having amismatch of −2.6% (thickness: 0.05 μm, Zn doping: 1×10¹⁸ cm⁻³), a secondintermediate band gap layer 165B having a mismatch of −2.8% (thickness:0.05 μm, Zn doping: 1×10¹⁸ cm⁻³), and a third intermediate band gaplayer 165C having a mismatch of −3.0% (thickness: 0.05 μm, Zn doping:1×10¹⁸ cm⁻³), in this order from below.

[0198] With this semiconductor light-emitting device of the ninthembodiment, the operating voltage at 20 mA was 1.90 V, smaller ascompared with the semiconductor light-emitting device of the seventhembodiment. The reason of this is that, as can be understood from theband junction diagram shown in FIG. 14, the notch height at the junctionis further divided and decreased.

[0199] Although the ninth embodiment has been described with respect toa semiconductor light-emitting device in which the number ofintermediate band gap layers are has been set to 3 layers, yet thenumber of intermediate band gap layers may be an arbitrary number (2layers or more).

Tenth Embodiment

[0200] The semiconductor light-emitting device of a tenth embodiment ofthe invention differs from the semiconductor light-emitting device ofthe seventh embodiment in that the second-conductive-type protectivelayer is a p-Al_(0.05)Ga_(0.9)In_(0.5)P layer.

[0201] In this semiconductor light-emitting device of the tenthembodiment, although the ground of the regrown interface in the regionthrough which the current flows is given by a layer containing Al, the20 mA operating voltage is 2.0 V because the Al content as small as 5%on the basis of a total of the III group. The resulting operatingvoltage is the same as in the semiconductor light-emitting device of theseventh embodiment.

[0202] When this semiconductor light-emitting device of the tenthembodiment was applied to a 5 mm dia. molded article, the emissionintensity at a 20 mA conduction was 3.0 cd, the same as in thesemiconductor light-emitting device of the first embodiment.

[0203]FIG. 15 shows the 20 mA operating voltage of the semiconductorlight-emitting device of the seventh embodiment resulting when the Alcomposition ratio of the second-conductive-type AlGaInP protective layeris varied. As apparent from FIG. 15, the operating voltage of thissemiconductor light-emitting device of the tenth embodiment is 0.07 ormore lower than that in the case where the protective layer is notprovided (first embodiment, in which the 20 mA operating voltage is 2.1V). Consequently, the Al composition ratio X of the p-AlGaInP protectivelayer is, desirably, not more than 0.2 (not more than 20%) as acondition for the operating voltage to be not more than 2.03 V.

Eleventh Embodiment

[0204] The semiconductor light-emitting device which is an eleventhembodiment of the invention differs from the semiconductorlight-emitting device of the first embodiment in that the secondcladding layer is a p-Al_(0.5)In_(0.5)P layer.

[0205] In this semiconductor light-emitting device of the eleventhembodiment, the notch occurring at the valence band between the currentdiffusion layer and the second cladding layer shown in the band junctiondiagram of FIG. 2B is even higher (about 0.29 eV) than that of thesemiconductor light-emitting device of the first embodiment. As aresult, the 20 mA operating voltage at this interface increases to about3.7 V (against about 3.5 V of the first embodiment).

[0206] On the other hand, the notch occurring at the valence bandbetween the intermediate band gap layer and the second cladding layershown in the band junction of FIG. 2C also becomes higher (about 0.16eV) than that of the semiconductor light-emitting device of the firstembodiment. However, the resultant increase of the 20 mA operatingvoltage is only about 0.05 V.

[0207] Consequently, in this semiconductor light-emitting device,although the 20 mA operating voltage became 2.15 V, being 0.05 V higherthan that of the semiconductor light-emitting device of the firstembodiment, yet this is no problem practically.

[0208]FIG. 16 shows the 20 mA operating voltage resulting when the Alcomposition ratio X of the p-(Al_(x)Ga_(1−x))_(0.5)In_(0.5)P secondcladding layer was varied. In this case, the intermediate band gap layerwas given by a layer having a mismatch of −3.1% to GaAs. With the Alcomposition being not less than 0.6, the operating voltage was not morethan 2.5 V, which is a permissible level. On the other hand, with the Alcomposition ratio X being less than 0.6, the emission intensitydecreases (which would be attributed to the fact that a hetero-barrierbetween p-cladding layer and active layer cannot be obtained). Thus, theAl composition is desirably within a range of 0.6≦X≦1.0.

[0209] Also, FIG. 17 shows the 20 mA operating voltage resulting whenthe layer thickness of the intermediate layer was varied in thesemiconductor light-emitting device of the seventh embodiment shown inFIG. 8. As can be understood from FIG. 17, since the operating voltageincreases beyond 2.5 V with the intermediate layer thickness beyond 0.5μm, the thickness of the intermediate layer is desirably not more than0.5 μm. The reason that the operating voltage increases with increasingthickness of the intermediate layer can be considered that a resistancecomponent of the intermediate layer itself emerges.

[0210] Also, FIG. 18 shows the 20 mA operating voltage resulting whenthe carrier concentration of the intermediate layer was varied in thesemiconductor light-emitting device of the seventh embodiment shown inFIG. 8. As can be understood from FIG. 18, since the operating voltageincreases beyond 2.5 V with the carrier concentration of theintermediate layer being under 0.5×10¹⁸ cm⁻³, the carrier concentrationof the intermediate layer is desirably not less than 0.5×10¹⁸ cm⁻³. Thereason that the operating voltage increases with decreasing carrierconcentration of the intermediate layer can be considered that seriesresistance of the notch part increases.

Twelfth Embodiment

[0211]FIGS. 19A, 19B, 19C and 19D show a semiconductor light-emittingdevice manufacturing method according to the present invention.

[0212] First, an n-GaAs buffer layer 181 with a thickness of 0.5 μm (Sidoping: 5×10¹⁷ cm⁻³), an n-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P firstcladding layer 182 with a thickness of 1.0 μm (Si doping: 5×10¹⁷ cm⁻³)an undoped (Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 183 with athickness of 0.6 μm, a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P secondcladding layer 184 with a thickness of 0.7 μm (Zn doping: 5×10¹⁷ cm⁻³),a p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)P intermediate band gap layer 185with a thickness of 0.15 μm, and a p-GaP protective layer 186 with athickness of 0.1 μm (Zn doping: 1×10¹⁸ cm⁻³) are stacked one by one onan n-GaAs substrate 190 by MOCVD process (FIG. 19A).

[0213] Subsequently, a pattern is formed with an ordinary photomask, andthen device center regions of the protective layer 186 and theintermediate band gap layer 185 are removed by etching, by which aprotective layer 186A and an intermediate band gap layer 185A eachhaving a circular-shaped removal region are formed (FIG. 19B).

[0214] For example, the 0.1 μm thick p-GaP protective layer 186 can beetched by being dipped for about 1 min. in a solution (50° C.) ofH₂SO₄:H₂O₂:H₂O=3:1:1, and the p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)Pintermediate band gap layer 185 can also be etched by being dipped forabout 2 min. in the same solution.

[0215] Thereafter, a p-GaP current diffusion layer 187 (Zn doping:2×10¹⁸ cm⁻³) is grown to a thickness of 6 μm also by MOCVD process (FIG.19C).

[0216] Next, a first electrode 191 is formed overall under the n-GaAssubstrate 190, while a circular-shaped second electrode 192 is formedover the grown-layer side device center region opposite to the removalregion (FIG. 19D). This grown-layer side second electrode 192 may beformed either by forming an electrode overall on the grown layer sideand then using an ordinary photomask, or by selectively depositing theelectrode with a metal mask.

[0217] With the use of this semiconductor light-emitting devicemanufacturing method, a heterojunction of type II by thep-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 184 and thep-GaP current diffusion layer 187 is formed, so that a high-resistanceinterface can be formed.

[0218] In this case, the n-type first cladding layer 182, the activelayer 183 and the p-type second cladding layer 184 need only to beAlGaInP layers that provide lattice matching with GaAs. Also, the p-GaPcurrent diffusion layer 187 needs only to be a semiconductor that formsa heterojunction of type II with the p-type second cladding layer 184.

Thirteenth Embodiment

[0219]FIGS. 20A, 20B, 20C and 20D show a semiconductor light-emittingdevice manufacturing method which is a thirteenth embodiment of theinvention.

[0220] First, an n-GaAs buffer layer 201 with a thickness of 0.5 μm (Sidoping: 5×10¹⁷ cm⁻³), an n-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P firstcladding layer 202 with a thickness of 1.0 μm (Si doping: 5×10¹⁷ cm⁻³)an undoped (Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 203 with athickness of 0.6 μm, a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P secondcladding layer 204 with a thickness of 0.7 μm (Zn doping: 5×10¹⁷ cm⁻³),a p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)P intermediate band gap layer 205with a thickness of 0.15 μm, and a p-GaP protective layer 206 with athickness of 0.1 μm (Zn doping: 1×10¹⁸ cm⁻³) are stacked one by one onan n-GaAs substrate 210 by MOCVD process (FIG. 20A).

[0221] Subsequently, a pattern is formed with an ordinary photomask, andthen device center regions of the protective layer 206 and theintermediate band gap layer 205 are removed by etching, and further a0.4 μm thick upper portion of the p-AlGaInP second cladding layer 204corresponding to the above removal regions is removed by etching. Thus,a protective layer 206A, an intermediate band gap layer 205A and asecond cladding layer 204A each having a circular-shaped removal regionare formed (FIG. 20B).

[0222] For example, the 0.1 μm thick p-GaP protective layer 206 can beetched by being dipped for about 1 min. in a solution (50° C.) ofH₂SO₄:H₂O₂:H₂O=3:1:1, and the p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)Pintermediate band gap layer 205 can also be etched by being dipped forabout 2 min. in the same solution. Next, the p-AlGaInP second claddinglayer 204 can be etched to nearly a desired position (remainingthickness: 0.3 μm) by being dipped for about 4 min. in a H₃PO₄ undilutedsolution (40° C.).

[0223] Thereafter, a p-GaP current diffusion layer 207 (Zn doping:2×10¹⁸ cm⁻³) is grown to a thickness of 6 μm also by MOCVD process (FIG.20C).

[0224] Next, a first electrode 211 is formed overall under the n-GaAssubstrate 210, while a circular-shaped second electrode 212 is formedover the grown-layer side device center region (FIG. 20D). Thegrown-layer side second electrode 212 may be formed either by forming anelectrode overall on the grown layer side and then using an ordinaryphotomask, or by selectively depositing the electrode with a metal mask.

[0225] With the use of this semiconductor light-emitting devicemanufacturing method, a heterojunction of type II by thep-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 204 and thep-GaP current diffusion layer 207 is formed, so that a high-resistanceinterface can be formed.

[0226] In this case, the n-type first cladding layer 202, the activelayer 203 and the p-type second cladding layer 204 need only to beAlGaInP layers that provide lattice matching with GaAs.

[0227] Also, the current diffusion layer 207 needs only to be asemiconductor that forms a heterojunction of type II with the p-typesecond cladding layer 204.

Fourteenth Embodiment

[0228]FIGS. 21A, 21B, 21C and 21D show a semiconductor light-emittingdevice manufacturing method which is a thirteenth embodiment of theinvention.

[0229] First, an n-GaAs buffer layer 221 with a thickness of 0.5 μm (Sidoping: 5×10¹⁷ cm⁻³), an n-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P firstcladding layer 222 with a thickness of 1.0 μm (Si doping: 5×10¹⁷ cm⁻³),an undoped (Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 223 with athickness of 0.6 μm and a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P secondcladding layer 224 with a thickness of 0.3 μm (Zn doping: 5×10¹⁷ cm⁻³)are stacked on an n-GaAs substrate 230 by MOCVD process. Then, ap-Ga_(0.5)In_(0.5)P etching stop layer 225 with a thickness of 0.01 μm(Zn doping: 5×10¹⁷ cm⁻³), a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P thirdcladding layer 226 with a thickness of 0.4 μm (Zn doping: 5×10¹⁷ cm⁻³),a p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)P intermediate band gap layer 227with a thickness of 0.15 μm, and a p-GaP protective layer 228 with athickness of 0.1 μm (Zn doping: 1×10¹⁸ cm⁻³) are stacked one by one(FIG. 21A).

[0230] Subsequently, a pattern is formed with an ordinary photomask, andthen device center regions of the protective layer 228, the intermediateband gap layer 227 and the p-AlGaInP third cladding layer 226 areremoved by etching, by which a protective layer 228A, an intermediateband gap layer 227A and a third cladding layer 226A each having acircular-shaped removal region are formed (FIG. 21B).

[0231] For example, the 0.1 μm thick p-GaP protective layer 228 can beetched by being dipped for about 1 min. in a solution (50° C.) ofH₂SO₄:H₂O₂:H₂O=3:1:1, and the p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)Pintermediate band gap layer 227 can also be etched by being dipped forabout 2 min. in the same solution. Next, the 0.4 μm thick p-AlGaInPthird cladding layer 226 can be completely etched by being dipped forabout 5 min. in a H₃PO₄ undiluted solution (40° C.). As to the reason ofthis, although the 0.4 μm thick p-AlGaInP third cladding layer 226 canbe generally etched in four min. as described in the semiconductorlight-emitting device manufacturing method of the thirteenth embodiment,yet the p-GaInP layer contributes as the etching stop layer 225 andtherefore the p-AlGaInP third cladding layer 226 is dipped somewhatlonger so that etching irregularities can be eliminated.

[0232] Thereafter, a p-GaP current diffusion layer 229 (Zn doping:2×10¹⁸ cm⁻³) is grown to a thickness of 6 μm also by MOCVD process (FIG.21C).

[0233] Next, a first electrode 231 is formed overall under the n-GaAssubstrate 230, while a circular-shaped second electrode 232 is formedover the grown-layer side device center region (FIG. 21D). Thegrown-layer side second electrode 232 may be formed either by forming anelectrode overall on the grown layer side and then using an ordinaryphotomask, or by selectively depositing the electrode with a metal mask.

[0234] With the use of this semiconductor light-emitting devicemanufacturing method, a heterojunction of type II by thep-Ga_(0.5)In_(0.5)P etching stop layer 225 and the p-GaP currentdiffusion layer 229 is formed, so that a high-resistance interface canbe formed.

[0235] In this case, the n-type first cladding layer 222, the activelayer 223, the p-type second cladding layer 224 and the third claddinglayer 226 need only to be AlGaInP layers that provide lattice matchingwith GaAs. Also, the current diffusion layer 229 needs only to be asemiconductor that forms a heterojunction of type II with the secondcladding layer 224.

Fifteenth Embodiment

[0236]FIGS. 22A, 22B, 22C and 22D show a semiconductor light-emittingdevice manufacturing method which is a fifteenth embodiment of theinvention.

[0237] First, by MOCVD process, on an n-GaAs substrate 250 is grown ann-GaAs buffer layer 241 (Si doping: 5×10¹⁷ cm⁻³) to a thickness of 0.5μm, and then, ten pairs of n-Al_(0.5)In_(0.5)P layer andn-(Al_(0.4)Ga_(0.6))_(0.5)In_(0.5)P layer are further formed, by which aDBR (optical reflection) layer 242 is formed (thickness of each layer:0.05 μm, Si doping of each layer: 5×10¹⁷ cm⁻³) Subsequently, ann-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first cladding layer 243 with athickness of 1.0 μm (Si doping: 5×10¹⁷ cm⁻³), an undoped(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 244 with a thickness of0.6 μm, a p-(Al_(0.7)Ga_(0.3))_(0.5)In₅P second cladding layer 245 witha thickness of 0.7 μm (Zn doping: 5×10¹⁷ cm⁻³), ap-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)P intermediate band gap layer 246 witha thickness of 0.15 μm, and a p-GaP protective layer 247 with athickness of 0.1 μm (Zn doping: 1×10¹⁸ cm⁻³) are stacked one by one(FIG. 22A)

[0238] Subsequently, a pattern is formed with an ordinary photomask, andthen regions of the protective layer 247 and the intermediate band gaplayer 246 other than their device center regions are removed by etching,by which circular-shaped protective layer 247A and intermediate band gaplayer 246A are formed (FIG. 22B).

[0239] For example, the 0.1 μm thick p-GaP protective layer 247 can beetched by being dipped for about 1 min. in a solution (50° C.) ofH₂SO₄:H₂O₂:H₂O=3:1:1, and the p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)Pintermediate band gap layer 246 can also be etched by being dipped forabout 2 min. in the same solution.

[0240] Thereafter, a p-(Al_(0.05)Ga_(0.95))_(0.9)In_(0.1)P currentdiffusion layer 248 (Zn doping: 2×10¹⁸ cm⁻³) is grown to a thickness of6 μm also by MOCVD process (FIG. 22C).

[0241] Next, a first electrode 251 is formed overall under the n-GaAssubstrate 250, while a second electrode 252 is formed over the regionother than the device center region on the grown layer side (FIG. 22D).The grown-layer side second electrode 252 may be formed either byforming an electrode overall on the grown layer side and then using anordinary photomask, or by selectively depositing the electrode with ametal mask.

[0242] With the use of this semiconductor light-emitting devicemanufacturing method, a heterojunction of type II by thep-(Al_(0.7)Ga_(0.3)) _(0.5)In_(0.5)P second cladding layer 245 and thep-(Al_(0.05)Ga_(0.95))_(0.9)In_(0.5)P current diffusion layer 248 isformed, so that a high-resistance interface can be formed.

[0243] In this case, the n-type first cladding layer 243, the activelayer 244 and the p-type second cladding layer 245 need only to beAlGaInP layers that provide lattice matching with GaAs. Also, thecurrent diffusion layer 248 needs only to be a semiconductor that formsa heterojunction of type II with the p-type second cladding layer 245.

Sixteenth Embodiment

[0244]FIGS. 23A, 23B, 23C and 23D show a semiconductor light-emittingdevice manufacturing method which is a sixteenth embodiment of theinvention.

[0245] First, by MOCVD process, on an n-GaAs substrate 270 is grown ann-GaAs buffer layer 261 (Si doping: 5×10¹⁷ cm⁻³) to a thickness of 0.5μm, and then, ten pairs of n-Al_(0.5)In_(0.5)P layer andn-(Al_(0.4)Ga_(0.6))_(0.5)In_(0.5)P layer are further formed, by which aDBR layer 262 is formed (thickness of each layer: 0.05 μm, Si doping ofeach layer: 5×10¹⁷ cm⁻³) Subsequently, ann-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first cladding layer 263 with athickness of 1.0 μm (Si doping: 5×10¹⁷ cm⁻³), an undoped(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 264 with a thickness of0.6 μm, a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 265with a thickness of 0.7 μm (Zn doping: 5×10¹⁷ cm⁻³), ap-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)P intermediate band gap layer 266 witha thickness of 0.15 μm, and a p-GaP protective layer 267 with athickness of 0.1 μm (Zn doping: 1×10¹⁸ cm-⁻³) are stacked one by one(FIG. 23A).

[0246] Subsequently, a pattern is formed with an ordinary photomask, andthen regions of the protective layer 267 and the intermediate band gaplayer 266 other than their device center regions are removed by etching,and a 0.3 μm thick upper portion of the p-AlGaInP second cladding layer265 corresponding to the above removal regions is removed by etching(FIG. 23B).

[0247] For example, the 0.1 μm thick p-GaP protective layer 267 can beetched by being dipped for about 1 min. in a solution (50° C.) ofH₂SO₄:H₂O₂:H₂O=3:1:1, and the p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)Pintermediate band gap layer 266 can also be etched by being dipped forabout 2 min. in the same solution. Next, the p-AlGaInP second claddinglayer 265 can be etched generally to a desired position (remainingthickness: 0.3 μm) by being dipped for about 4 min. in a H₃PO₄ undilutedsolution (40° C.)

[0248] Thereafter, a p-(Al_(00.5)Ga_(0.95))_(0.9)In_(0.1)P currentdiffusion layer 268 (Zn doping: 2×10¹⁸ cm⁻³) is grown to a thickness of6 μm also by MOCVD process (FIG. 23C).

[0249] Next, a first electrode 271 is formed overall under the n-GaAssubstrate 270, while a second electrode 272 is formed over the regionother than the device center region on the grown layer side (FIG. 23D).The grown-layer side second electrode 272 may be formed either byforming an electrode overall on the grown layer side and then using anordinary photomask, or by selectively depositing the electrode with ametal mask.

[0250] With the use of this semiconductor light-emitting devicemanufacturing method, a heterojunction of type II by thep-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer 265 and thep-(Al_(00.5)Ga_(0.95))_(0.9)In_(0.1)P current diffusion layer 269 isformed, so that a high-resistance interface can be formed.

[0251] In this case, the n-type first cladding layer 263, the activelayer 264 and the p-type second cladding layer 265 need only to beAlGaInP layers that provide lattice matching with GaAs. Also, thecurrent diffusion layer 268 (269) needs only to be a semiconductor thatforms a heterojunction of type II with the p-type second cladding layer265.

Seventeenth Embodiment

[0252]FIGS. 24A, 24B, 24C and 24D show a semiconductor light-emittingdevice manufacturing method which is a seventeenth embodiment of theinvention.

[0253] First, by MOCVD process, on an n-GaAs substrate 290 is grown ann-GaAs buffer layer 281 (Si doping: 5×10¹⁷ cm⁻³) to a thickness of 0.5μm, and then, ten pairs of n-Al_(0.5)In_(0.5)P layer andn-(Al_(0.4)Ga_(0.6))_(0.5)In_(0.5)P layer are further formed, by which aDBR layer 282 is formed (thickness of each layer: 0.05 μ, Si doping ofeach layer: 5×10¹⁷ cm⁻³). Subsequently, ann-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P first cladding layer 283 with athickness of 1.0 μm (Si doping: 5×10¹⁷ cm⁻³), an undoped(Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P active layer 284 with a thickness of0.6 μm, and a p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P second cladding layer285 with a thickness of 0.3 μm (Zn doping: 5×10¹⁷ cm⁻³) are stacked oneby one. After this, a p-Ga_(0.5)In_(0.5)P etching stop layer 286 with athickness of 0.01 μm (Zn doping: 5×10¹⁷ cm⁻³), ap-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P third cladding layer 287 with athickness of 0.4 μm (Zn doping: 5×10¹⁷ cm⁻³), ap-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)P intermediate band gap layer 288 witha thickness of 0.15 μm, and a p-GaP protective layer 289 with athickness of 0.1 μm (Zn doping: 1×10¹⁸ cm⁻³) are stacked one by one(FIG. 24A).

[0254] Subsequently, a pattern is formed with an ordinary photomask, andthen regions of the protective layer 289, the intermediate band gaplayer 288 and the p-AlGaInP third cladding layer 287 other than theirdevice center regions are removed by etching, by which circular-shapedprotective layer 289A, intermediate band gap layer 288A and thirdcladding layer 287A are formed (FIG. 24B).

[0255] For example, the 0.1 μm thick p-GaP protective layer 289 can beetched by being dipped for about 1 min. in a solution (50° C.) ofH₂SO₄:H₂O₂:H₂O=3:1:1, and the p-(Al_(0.4)Ga_(0.6))_(0.9)In_(0.1)Pintermediate band gap layer 288 can also be etched by being dipped forabout 2 min. in the same solution. Next, the 0.4 μm p-AlGaInP thirdcladding layer 287 can be completely etched by being dipped for about 5min. in a H₃PO₄ undiluted solution (40° C.). As to the reason of this,although the 0.4 μm thick p-AlGaInP third cladding layer 287 can begenerally etched in four min. as described in the semiconductorlight-emitting device manufacturing method of the sixteenth embodiment,yet the p-GaInP layer contributes as the etching stop layer 286 andtherefore the p-AlGaInP third cladding layer 287 is dipped somewhatlonger so that etching irregularities can be eliminated.

[0256] Thereafter, a p-(Al_(0.05)Ga_(0.95))_(0.9)In_(0.1)P currentdiffusion layer 293 (Zn doping: 2×10¹⁸ cm⁻³) is grown to a thickness of6 μm also by MOCVD process (FIG. 24C).

[0257] Next, a first electrode 291 is formed overall under the n-GaAssubstrate 290, while a second electrode 272 is formed over the regionother than the device center region on the grown layer side (FIG. 24D).The grown-layer side second electrode 292 may be formed either byforming an electrode overall on the grown layer side and then using anordinary photomask, or by selectively depositing the electrode with ametal mask.

[0258] With the use of this semiconductor light-emitting devicemanufacturing method, a heterojunction of type II by thep-Ga_(0.5)In_(0.5)P etching stop layer 286 and thep-(Al_(00.5)Ga_(0.95))_(0.9)In_(0.1)P current diffusion layer 293 isformed, so that a high-resistance interface can be formed.

[0259] In this case, the n-type first cladding layer 283, the activelayer 284 and the p-type second cladding layer 285 need only to beAlGaInP layers that provide lattice matching with GaAs. Also, thecurrent diffusion layer 293 needs only to be a semiconductor that formsa heterojunction of type II with the second cladding layer 285.

[0260] Although it has been assumed in the foregoing first toseventeenth embodiments that the first conductive type is n type and thesecond conductive type is p type, yet it is of course possible that thefirst conductive type is p type and the second conductive type is ntype.

[0261] Also, the first electrodes 11, 31, 51, 71, 91, 111, 131, 151,171, 191, 211, 231, 251, 271 and 291 have been formed overall on thesubstrates 10, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230, 250,270 and 290 in the foregoing first to seventeenth embodiments. However,those electrodes may be formed partly on the substrates.

[0262] Furthermore, although the second electrodes 12, 32, 52, 132, 152and 172 as well as the removal regions of the second electrodes 72, 92and 112 have been circular-shaped in the first to eleventh embodiments,yet the shape of the second electrodes is not limited to this and may beformed into other shapes such as quadrangular shapes.

[0263] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, a first electrode formed on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed partly on the second-conductive-type current diffusion layer, wherein a region of the second-conductive-type intermediate band gap layer just under the second electrode is removed, and the second-conductive-type current diffusion layer is stacked in the removal region on the second-conductive-type second cladding layer, and wherein a junction plane of the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer has an energy band structure of type II.
 2. A semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein a device center region of the second-conductive-type intermediate band gap layer is removed, and the second-conductive-type current diffusion layer is stacked in the removal region on the second-conductive-type second cladding layer, the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein the semiconductor light-emitting device further comprises a first electrode formed overall on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the device center region on the second-conductive-type current diffusion layer.
 3. The semiconductor light-emitting device according to claim 2, wherein an upper-side portion of a region of the second-conductive-type second cladding layer corresponding to the removal region of the second-conductive-type intermediate band gap layer is removed.
 4. A semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type etching stop layer, a second-conductive-type third cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein device center regions of the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer are removed, respectively, and the second-conductive-type current diffusion layer is stacked in the removal regions on the second-conductive-type etching stop layer, the second-conductive-type current diffusion layer, the second-conductive-type etching stop layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein the semiconductor light-emitting device further comprises a first electrode formed overall on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the device center region on the second-conductive-type current diffusion layer.
 5. The semiconductor light-emitting device according to claim 2, wherein the removal region at the device center region of the second-conductive-type intermediate band gap layer and the second electrode have generally identical configurations and are opposed to each other.
 6. A semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein a region of the second-conductive-type intermediate band gap layer other than its device center region is removed, and the second-conductive-type current diffusion layer is stacked in the removal region on the second-conductive-type second cladding layer, the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein the semiconductor light-emitting device further comprises a first electrode formed overall on the other side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the region other than the device center region on the second-conductive-type current diffusion layer.
 7. The semiconductor light-emitting device according to claim 6, wherein an upper-side portion of the region of the second-conductive-type second cladding layer opposed to the removal region of the second-conductive-type intermediate band gap layer is removed.
 8. A semiconductor light-emitting device comprising: a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type etching stop layer, a second-conductive-type third cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type current diffusion layer, all of which are stacked on one side of a surface of a first-conductive-type semiconductor substrate, wherein regions of the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer other than their device center regions are removed, respectively, and the second-conductive-type current diffusion layer is stacked in the removal regions on the second-conductive-type etching stop layer, the second-conductive-type current diffusion layer, the second-conductive-type etching stop layer and the second-conductive-type second cladding layer have an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation, and wherein the semiconductor light-emitting device further comprises a first electrode formed overall on the one side of the surface of the first-conductive-type semiconductor substrate, and a second electrode formed over the region other than the device center region on the second-conductive-type current diffusion layer.
 9. The semiconductor light-emitting device according to claim 1, wherein a protective layer of the second conductive type is formed on the second-conductive-type intermediate band gap layer.
 10. The semiconductor light-emitting device according to claim 1, wherein the first-conductive-type semiconductor substrate is made of GaAs, the first-conductive-type first cladding layer, the first-conductive-type or second-conductive-type or undoped active layer and the second-conductive-type second cladding layer are made of an AlGaInP-based compound semiconductor that provides lattice matching with GaAs, the second-conductive-type current diffusion layer is made of a GaP- or AlGaInP-based compound semiconductor, and the second-conductive-type intermediate band gap layer is made of an AlGaInP-based compound semiconductor.
 11. The semiconductor light-emitting device according to claim 4, wherein the first-conductive-type semiconductor substrate is made of GaAs, the first-conductive-type first cladding layer, the first-conductive-type or second-conductive-type or undoped active layer, the second-conductive-type second cladding layer, the second-conductive-type etching stop layer 45 and the second-conductive-type third cladding layer are made of an AlGaInP-based compound semiconductor that provides lattice matching with GaAs, the second-conductive-type current diffusion layer is made of a GaP- or AlGaInP-based compound semiconductor, and the second-conductive-type intermediate band gap layer is made of an AlGaInP-based compound semiconductor.
 12. The semiconductor light-emitting device according to claim 10, wherein the second-conductive-type intermediate band gap layer made of the AlGaInP-based compound semiconductor has a rate Δa/a of lattice matching to GaAs falling within a range of −3.2%≦Δa/a≦−2.5%.
 13. The semiconductor light-emitting device according to claim 12, wherein the second-conductive-type intermediate band gap layer is composed of a plurality of AlGaInP layers having different rates of lattice matching to GaAs, the lattice matching rates Δa/a of those AlGaInP layers each falling within a range of −3.2≦Δa/a≦−2.5%.
 14. The semiconductor light-emitting device according to claim 10, wherein a second-conductive-type protective layer made of GaP or an AlGaInP-based compound semiconductor having a Al composition ratio of not more than 20% relative to the total of III group is stacked on the second-conductive-type intermediate band gap layer.
 15. The semiconductor light-emitting device according to claim 11, wherein the second-conductive-type second cladding layer and the second-conductive-type third cladding layer both made of an AlGaInP-based compound semiconductor have a composition of (Al_(x)Ga_(1−x))_(0.5)In_(0.5)P (where 0.6≦X≦1.0).
 16. The semiconductor light-emitting device according to claim 1, wherein the second-conductive-type intermediate band gap layer has a layer thickness of not more than 0.5 μm.
 17. The semiconductor light-emitting device according to claim 1, wherein the second-conductive-type intermediate band gap layer has a carrier concentration of not less than 0.5×10¹⁸ cm⁻³.
 18. A method for manufacturing a semiconductor light-emitting device, comprising the steps of: stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer; removing a device center region of the second-conductive-type protective layer and a device center region of the second-conductive-type intermediate band gap layer, respectively, by etching; after the removal step of the second-conductive-type protective layer and intermediate band gap layer, stacking a current diffusion layer on the second-conductive-type protective layer and the second-conductive-type second cladding layer to form, in the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation; forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and forming a second electrode over the device center region on the second-conductive-type current diffusion layer.
 19. A method for manufacturing a semiconductor light-emitting device, comprising the steps of: stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer; removing a device center region of the second-conductive-type protective layer and a device center region of the second-conductive-type intermediate band gap layer, respectively, by etching, and further removing an upperside portion of a region of the second-conductive-type second cladding layer corresponding to the removal region by etching; after the removal step of the second-conductive-type protective layer, intermediate band gap layer and second cladding layer, stacking a second-conductive-type current diffusion layer on the second-conductive-type protective layer and the second-conductive-type second cladding layer to form, in the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation; forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and forming a second electrode over the device center region on the second-conductive-type current diffusion layer.
 20. A method for manufacturing a semiconductor light-emitting device, comprising the steps of: stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type etching stop layer, a second-conductive-type third cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer; removing device center regions of the second-conductive-type protective layer, the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer by etching; after the removal step of the second-conductive-type protective layer, intermediate band gap layer and third cladding layer, stacking a second-conductive-type current diffusion layer on the second-conductive-type protective layer and the second-conductive-type etching stop layer to form, in the second-conductive-type current diffusion layer, the second-conductive-type etching stop layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation; forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and forming a second electrode over the device center region on the second-conductive-type current diffusion layer.
 21. A method for manufacturing a semiconductor light-emitting device, comprising the steps of: stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer; removing regions of the second-conductive-type protective layer and the second-conductive-type intermediate band gap layer other than their device center regions, respectively, by etching; after the removal step of the second-conductive-type protective layer and intermediate band gap layer, stacking a second-conductive-type current diffusion layer on the second-conductive-type protective layer and the second-conductive-type second cladding layer to form, in the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation; forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and forming a second electrode over the region other than the device center region on the second-conductive-type current diffusion layer.
 22. A method for manufacturing a semiconductor light-emitting device, comprising the steps of: stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer; removing regions of the second-conductive-type protective layer and the second-conductive-type intermediate band gap layer other than their device center regions, respectively, by etching, and further removing an upper-side portion of a region of the second-conductive-type second cladding layer corresponding to the removal region by etching; after the removal step of the second-conductive-type protective layer, intermediate band gap layer and second cladding layer, stacking a second-conductive-type current diffusion layer on the second-conductive-type protective layer and the second-conductive-type second cladding layer to form, in the second-conductive-type current diffusion layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation; forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and forming a second electrode over the region other than the device center region on the second-conductive-type current diffusion layer.
 23. A method for manufacturing a semiconductor light-emitting device, comprising the steps of: stacking, one by one on one side of a surface of a first-conductive-type semiconductor substrate, a first-conductive-type first cladding layer, a first-conductive-type or second-conductive-type or an undoped active layer, a second-conductive-type second cladding layer, a second-conductive-type etching stop layer, a second-conductive-type third cladding layer, a second-conductive-type intermediate band gap layer and a second-conductive-type protective layer; removing regions of the second-conductive-type protective layer, the second-conductive-type intermediate band gap layer and the second-conductive-type third cladding layer other than their device center regions, respectively, by etching; after the removal step of the second-conductive-type protective layer, intermediate band gap layer and third cladding layer, stacking a second-conductive-type current diffusion layer on the second-conductive-type protective layer and the second-conductive-type etching stop layer to form, in the second-conductive-type current diffusion layer, the second-conductive-type etching stop layer and the second-conductive-type second cladding layer, an energy band structure in which an upper-end position of valence band and a lower-end position of conduction band are in a type II relation; forming a first electrode overall on the other side of the surface of the first-conductive-type semiconductor substrate; and forming a second electrode over the region other than the device center region on the second-conductive-type current diffusion layer. 